Multilayer pH-Responsive Hydrogels Upcycled From Carrageenan-Based Capsule Residues for Colon-Targeted Delivery of 5-Aminosalicylic Acid.

Authors

Hoai-Khang Tran, Tien-Ngo Van, Hong Ha Nguyen, Thi Thuy Hang Hoang, Ngoc Hai Vu, Colin J Barrow, Hoang Chinh Nguyen

Published in

Journal of biomedical materials research. Part A. Volume 114. Issue 11.

Abstract

Softgel capsule manufacturing generates substantial carrageenan-containing byproducts that are typically discarded, despite their intrinsic gel-forming and polyelectrolyte-complexing capability. This study reports a sustainable strategy for upcycling carrageenan-based capsule residues (CCR) into multilayer pH-responsive hydrogel beads for colon-targeted delivery of 5-aminosalicylic acid (5-ASA). CCR hydrogel cores were prepared by K⁺-mediated ionotropic gelation, followed by sequential coating with chitosan and alginate to form double-layer (CCR/Cs) and triple-layer (CCR/Cs/Alg) beads. Morphological and structural analyses suggested successful layer formation and interfacial interactions. The layer-by-layer assembly substantially enhanced network stability, increasing the gel fraction from 52% for CCR to 78% for CCR/Cs/Alg beads. In simulated gastric fluid (pH 1.2), CCR and CCR/Cs released 56.93% and 60.41% of 5-ASA, respectively, whereas CCR/Cs/Alg limited release to 28.09%, demonstrating superior acid resistance. Under simulated intestinal (pH 6.8) and colonic (pH 7.4) conditions, CCR/Cs/Alg beads exhibited a controlled, stepwise drug release, reaching 45.88% at 5 h and 70.16% at 8 h. Release kinetics were best fitted by the Korsmeyer-Peppas model (R² = 0.9928, n = 0.7480), suggesting contributions from both drug diffusion and polymer-network relaxation to the observed release behavior. These findings demonstrate that carrageenan-based capsule residues can serve as a primary structural feedstock for fabricating multilayer pH-responsive hydrogels with gastric protection and controlled drug release. This work also provides a value-added pathway for converting pharmaceutical manufacturing residues into functional biomaterials for targeted drug delivery.

PMID:
42989740
Bibliographic data and abstract were imported from PubMed on 06 Nov 2026.

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